Climate Implications – Wetlands

Wetlands are important features in the landscape that provide numerous beneficial services for people and for fish and wildlife. Some of these services, or functions, include protecting and improving water quality, providing fish and wildlife habitats, storing floodwaters and maintaining surface water flow during dry periods.

Climate changes such as drought, warmer temperatures and changing precipitation patterns can all affect the health and beneficial functionality of wetlands. Sea level rise and wildfires can further impact wetlands, in areas of the country where those changes are happening. Climate changes in combination with other stressors, such as land development, may further exacerbate the loss of wetlands.

Warmer temperatures, drought and changing precipitation patterns can increase evapotranspiration and lead to water losses. Drought can also increase events such as wildfires, which can alter water quality and the structure and function of wetlands and watersheds. Wetlands loss can also lead to reduced habitat for fish and wildlife and worsen existing shifts in species ranges. Wetlands managers need to understand these impacts and how to manage for healthy wetlands under these changing conditions.

In coastal areas, sea level rise will threaten to inundate or displace some coastal wetlands. Some coastal wetland types that may be vulnerable to climate change include salt marshes, bottomland hardwood swamps, fresh marshes, mangrove swamps, and shrubby depressions known in the southeast United States as "pocosins.“ Both tidal and non-tidal wetlands may be at risk from sea-level rise.  Sea-level-rise may introduce saltwater into non-tidal wetlands, which may be inhibited from moving inland due to coastal development. Climate change can inhibit the ability of sediment accretion in tidal wetlands leading to vegetation “drowning.”  A decrease in coastal wetlands can threat coastal estuary protection and restoration efforts.

Flood Management

Wetlands provide valuable flood storage, buffer storm surge and assist in erosion control. Wetlands function as natural sponges that trap and slowly release surface water, rain, snowmelt, groundwater and flood waters. Trees, root mats and other wetland vegetation also slow the speed of flood waters and distribute them more slowly over the floodplain. This combined water storage and braking action lowers flood heights and reduces erosion.

Wetlands within and downstream of urban areas are particularly valuable, counteracting the greatly increased rate and volume of surface-water runoff from pavement and buildings. The holding capacity of wetlands helps control floods and prevents water logging of crops. Preserving and restoring wetlands together with other water retention can often provide the level of flood control otherwise provided by expensive dredge operations and levees. The bottomland hardwood-riparian wetlands along the Mississippi River once stored at least 60 days of floodwater. Now they store only 12 days because most have been filled or drained.